Alginate salts and process of making same



Patented May 16, 1939 UNITED STATES PATENT OFFICE Bennett Preble, San Diego. Calm, minor to Kelco Company, Los Angeles, Call!., a cor-po tion of Delaware No Drawing. Original application October 22.

1935, Serial No. 46,213. plication December 30, 1937, Serial Claims.

This application is a division of my application for patent on Amine alginate product and process flied October 22, 1935, Serial No. 46,213,

and is filed in compliance with the oflicial requirement for division of said application. The present application relates more particularly to a mixed salt of an ethanolamine and organic substituents and process of producing same.

The product is a water soluble hydroxy salt of alginic acid as set forth in the appended claims, said product having many novel and valuable properties, rendering same useful for many purposes in the arts. 1

I have discovered that triethanolamine, diethanolamine and monoethanolaminemay be used in producing water soluble products from alginic acid. Furthermore, since triethanolamine is a hydroxy amine, other hydroxy amines, such as tripropanolamines, dipropanolamines and monopropanolamines may replace any of the ethanolamines. Complicated hydroxy amines for example the butanolamines, may be used. In addition, amines other than hydroxy amines, for example, simple aliphatic, tertiary, secondary or primary amines, such as tripentyl amines, dipentyl amines and monopentylamines, also substituted amines, including chlorinated amines,.

may replace triethanolamine. These replacements of ethanolamines may be complete or partial or may be made by more than-one amine. Commercial monoethanolamlne is principally NI-I2C2H4OH (2-amino-ethanol); commercial diethanolamine is vmainly NH(C2H4OH)2: and commercial triethanolamine is mainly N(C2H4OH): (5,;9',B"-trihydroxytriethylamine) The commercial grade of each of these contains a small amount of the other two, but so far we have found the best results are obtained for our purposes when using triethanolamine.

When technical triethanolamine and alginic acid are mixed in the approximate proportions of their respective equivalent weights a neutral product is obtained and hence the reaction which occurs when alglnic acid and triethanolamine are mixed is probably expressed, as far as I have at present been able to ascertain, by the following theoretical equation:-

Triethanolamine Alginic acid Triethanolamine alglna Molecular and Equivalent equivalent wt.=149 weight=l76 The triethanolamine I have used in the manufacture of this composition is a commercial grade Divided and this apmade by the Carbide and Carbon Chemical Corporation, and consists of about 87% triethanolamine, 11% diethanolamine and 2% monoethanolamine.

The alginic acid used in manufacturing this composition may be any alginic acid, although I prefer that manufactured by the method disclosed in the Thornley & Walsh U. S. Letters Patent No. 1,814,981 issued July 14, 1931; or the Clark and Green application Serial No. 693,891, filed October 16, 1933; or the Green application Serial No. 721,829, filed April 21, 1934, since the alginic acid made by any of the said methods is relatively pure.

The following is one method for preparing the composition (A) Approximately 1000 lbs. of wet alglnic acid manufactured by the method disclosed in the above mentioned Clark and Green application, Serial No. 693,891, is placed in a dough or other suitable paste mixer. This acid would contain about 10% (or 100 lbs.) of dry material if all the water were evaporated. This mixer is started and approximately 80 lbs. of commercial triethanolamine is added slowly. The triethanolamine reacts almost immediately on the fibrous mass in the mixer to produce a stlif or heavy paste. After about thirty minutes of mixing the reaction is complete and a dilute solution of the paste will have a pH value of approximately 7. This composition is relatively pure triethanolamine alginate.

Triethanolamine alginate paste in comparison with pastes made from gums, gelatin, casein, etc., will not spoil easily since it is resistant to the action of molds and microorganisms which produce liquefaction and decay, and therefore molds grow or develop thereon very slowly; and such paste, it stored at temperatures below 40 degrees Fahrenheit or if some preservative such as formaldehyde is added thereto, may be preserved indefinitely.

To obtain an ethanolamine alginate composition of desired consistency, I may use an acid whose ammonia salt when in a 2% aqueous solution has a viscosity ranging from one to several thousand seconds, as measured by the Woolwich viscosity test. This test measures the time re- Equivalent weight=325' quired for a inch diameter steel ball to fall 15 centimeters at centlgrade. Specific examples of how the viscosity of my triethanolamine alginate may be controlled are given in the following table showing how different acids give triethanolamine alginates of different viscoslties:--

Resulting trlgg y: 339 ethanolamine niurn s t gives a g afiamgx iscosity ofo v a viscosity of A trlethanolamine alginate having four seconds viscosity on a 2% solution will dry to produce a good film, whereas a triethanolamine alginate with 800 seconds viscosity would have to be diluted to such an extent that the resulting film would not give the desired results. Triethanolamine alginate having a higher viscosity is more desirable for some purposes, such as for producing a stronger film. Moreover, a high viscosity trlethanolamine alginate has less tendency to run off the surface to which it is applied before becoming dry.

(B) In one method in which ammonia may replace part of the triethanolamine to control the consistency and nature of a dried film approximately 1000 lbs. of wet alginic acid manufactured by the Clark and Green method (application Serial No. 693,891) is placed in a dough mixer as described in Example (A), and 70 lbs. of commercial triethanolamine is slowly added along with 10 lbs. of 26 Baum aqua ammonia. After about thirty minutes of mixing (different types of mixers will naturally require more or less time) the resulting product has a pH between '7 and 8 and is an ammonium-triethanolamine alginate. This gives a film of medium pliability which dries faster.

When it is desired to produce a composition having a softer and more flexible film, this may be done by adding more than the combining chemical equivalent weight of triethanolamine so that the pH of a water solution of the paste is higher than 7. I have found 8.0 pH particularly useful.

Sometimes when a smaller amount of triethanolamine is used so that the pH of the resulting paste is 6.0 or below such composition is a stiffer paste or has a higher viscosity for a given concentration than one say of 7.0 pH and therefore has certain advantages for particular uses.

The pH of these triethanolamine alginate products will range between pH 3 and pH 11.

When a film of triethanolamine alginate is dried it is smooth, soft and flexible, and feels plump to the fingers, is strong, and will not crack when bent sharply, and is readily soluble in water but insoluble in oils and greases.

The above enumerated properties are in sharp contrast to those of other alginate salts, such as sodium or ammonium alginates, which form relatively brittle hard films which will crack when bent sharply and which therefore cannot be successfully utilized. Because of its strongly adhesive properties the triethanolamine alginate may be used for coating practically all solid surfaces such as cheese, meats, and other food products, glass, metals, wood, plastics, ceramic ware and plaster.

For'greater ease in shipping and handling the triethanolamine alginate may be produced in a dry form by putting the pastes hereinbefore described in a mechanical drier of any conventional type, such as a drum drier. After drying, the product is reduced by means of a chopper or mill to a particle size that can be conveniently dissolved in water. In some cases the paste might be converted into a dilute solution and then dried by means of a spray drier.

Dry product (C) The following is one method for producing the product in dry form: Approximately 1000 lbs. of wet alginic acid is placed in a tank and diluted with water to about 1000 gallons. This mixture is then agitated while 80 lbs. of triethanolamine is added. The result is about a 2% solution of triethanolamine alginate. This mixture is then spray dried to give a fine powder containing 80% triethanolamine alginate and 20% water.

(D) Triethanolamine alginate may be produced by first drying the alginic acid and then adding triethanolamine to it; as for example:

Approximately 1000 lbs. of wet alginic acid containing about 10% (or 100 lbs.) of dry material (if all the water was evaporated) is placed on trays and set in the sun until dried down to about lbs. This material is ground to pass through a 30 mesh screen, and then placed in a mixer, and 90 lbs. of triethanolamine added, resulting in very stiff crumbly material having a pH of about 9.5 when made into a 2% solution. This method takes longer to complete, but produces a good composition. This method reduces the viscosity of the produce as drying the alginic acid reduces the viscosity of the resulting salts made from the acid, which reduction in viscosity is probably due to the depolymerization of the alginic acid.

I have also found that by mixing dextrin with triethanolamine alginate paste prior to drying, the drying time can be shortened, and the product is more brittle and grinds easier, and will go into solution faster.

I have also found that the addition of sucrose increases the adhesive properties under certain conditions and also increases the ease of solution. Besides sucrose and dextrine, other substances which do not react with or precipitate alginates may be used. Among these are starch, glucose, fructose, maltose, zylose, glycerin, or mixtures of these with each other; also gelatin and glue when so treated that they will not react with the triethanolaminealginate, may be used. Instead of glycerine I may add other polyhydroxy compounds, such as sorbitol or some dlhydroxy compound such as ethylene glycol, propylene glycol, or other glycol.

It is possible to replace a part of the triethanolamine by other basic substances and produce a composite composition containing some sodium, ammonium, aluminum, zinc, potassium or other alkali earth metal.

The dried triethanolamine alginate product can be made to dissolve in water even when calcium salts or other salts which form insoluble alginates 'are present, by adding to the triethanolamine an amount of trisodium phosphate equivalent to 4 to 10 percent of the weight of the anhy drous alginic acid. In place of trisodium phosphate its equivalents may be used, such as disodium phosphate, ammonium phosphate, sodium carbonate, and other such salts which form an insoluble calcium salt.

If desired a preservative may be incorporated in the compositio for example- (E) Approximately 1000 lbs. of wet alginic acid is placed in a dough mixer and 60 lbs. of tri- 5 ethanolamine is added to form a wet paste containing partially neutralized alginic acid. The *pH of such a paste is approximately 6. To this paste 1-1 lbs. of formaldehyde is added as a preservative. Besides formaldehyde, other pre- I0 ,servatives, including sodium benzoate, phenol,

sodium phenyl phenolate, may be used.

I have also found that it is possible to replace part of the triethanolamine by other basic substances and produce a composite composition con- 15 taining some sodium, ammonium, potassium or other metal which could form a water soluble alginate salt. Furthermore, combinations may be made with metals which form water insoluble alginates such as zinc, calcium, aluminum, copper 20 or other like. In such a compound, one or more of the acidic hydrogen atoms of the complicated alginic acid molecule (C5H'IO4COOI'D1: may be replaced by one of the metals above, instead of being combined with triethanolamine to form COONH (C2H4OH) a.

My triethanolamine alginate product has cer- 5 .tain properties which have special merit and is salt of alginic acid.

BENNE'I'I' PREBLE. 1O 

